The present invention relates to non-destructive inspection (NDI) instruments, and more particularly to an enhanced wireless eddy current probe which provides advanced functionality including embedded diagnostics, power saving modes of operation, onboard status monitoring, embedded setup memory, means for coil element selection and interconnection, and wireless communication to a remote instrument.
Any discussion of the related art throughout this specification should in no way be considered as an admission that such art is widely known or forms a part of the common general knowledge in the field.
Eddy current inspection is a well known NDI technique used to examine conductive materials. In a typical eddy current inspection operation, an eddy current array probe, comprising a plurality of coils, is placed adjacent to the surface of a material under inspection. At the start of an inspection operation, an NDI instrument coupled to said eddy current array probe energizes one or more coils within the array. This, in turn, induces a current in the material under inspection. One or more coils within the probe array then sense this induced current and provide a measurement signal to the NDI instrument. By measuring the current induced in a material under inspection, the impedance of said material can be calculated. Further, by tracking the impedance of a material under inspection as the probe is moved along the surface of said material (or, in some NDI operations, comparing the measured impedance to that of a stored reference), flaws and defects within said material can be found and analyzed.
In a typical prior art eddy current NDI system, an eddy current probe is comprised of one or more coil elements which are coupled to an NDI instrument through a probe cable. Typically, at least two connections are made through the probe cable for each coil element within the probe. A first connection is made such that the NDI system to which a probe is coupled will have means to provide an excitation signal to each coil element within the probe. A second connection is made such that each coil element within the probe has means to provide a measurement signal sensed by that coil element to the NDI system for processing and analysis. In more complex systems wherein a single coil element will be excited or used to sense an induced current more than once within a firing sequence, more than two connections may be required to an individual coil element.
In many inspection systems, due to the plurality of connections required between the eddy current probe and the NDI system, the interconnecting probe cable becomes complex, expensive, and, in many cases, prone to damage. Moreover, in many NDI inspection operations one or more inspection points are located in difficult to access locations. Such locations include, but are not limited to, inspection points located a large distance away from the NDI system, inspection points which are located within hazardous locations wherein an inspection operator would be at personal risk during an inspection operation, or inspection points located within a complex structure, wherein said inspection points cannot be physically accessed without disassembly of said structure. Within such an inspection operation, the length of the interconnecting probe cable—often constrained by cost and signal integrity restrictions—can become a significant limitation for said operation.
U.S. Pat. No. 7,039,362 to Filkins et al. teaches an NDI system which uses a wireless transceiver between an NDI system and an ultrasonic inspection probe. While Filkins teaches a system which effectively overcomes the limitations of probe cable length, his solution is limited to and strictly addresses an ultrasonic system and is limited to an “uplink” path (a wireless communication path which provides means for signal transfer from an NDI system to an ultrasonic inspection probe) which transmits “timing pulse signals” to the ultrasonic probe and a “downlink” path (a wireless communication path which provides means for signal transfer from an ultrasonic inspection probe to an NDI system) which transmits only “envelope information” extracted from measurement data obtained by an ultrasonic inspection probe.
Filikins' wireless measurement probe interconnection system, while adequate for the specific ultrasonic NDI operation he describes, is insufficient to meet the needs of an eddy current NDI operation. Such NDI operations require excitation signals to be provided to individual coil elements and sensed measurement signals to be provided to the one or more receiver elements within the NDI system simultaneously during an inspection operation. Also, most eddy current inspection operations require that the full content of one or more measured signals (as opposed to simply the “envelope” information of said measured signals) be provided to the NDI system for proper analysis and processing. Further, within an inspection system comprising a multiple element eddy current array probe, the individual coils within the array probe are required to be excited and used to sense induced currents within an material under inspection in a predetermined sequence (commonly referred to as a firing sequence). Filkins' “timing pulse signals” do not provide a valid means to execute such a firing sequence within an eddy current NDI system.
A technical paper entitled “Wireless Eddy Current Probe for Health Engine Monitoring (Phase II),” published in “Review of Quantitative Nondestructive Evaluation Vol. 25” in 2006, and authored by Graubard et al. teaches a wireless NDI system specially designed for eddy current inspection. While Graubard's system provides sufficient means for transmitting measurement signals from a coil within an eddy current inspection probe to a remote, wirelessly couple NDI system, it does not provide means for said inspection probe to receive control signals from said NDI system. Further, Graubard's system fails to teach means for executing higher level inspection functions, which are commonly required in most eddy current NDI operations, via this wireless interface. These higher level functions include, but are not limited to, executing a predetermined firing sequence on an eddy current array probe, balancing a probe prior to an inspection operation (that is, adjusting the measurement signal from each coil element such that said measurement signal will read zero in the impedance plane for a “good” measurement reading), and calibration of the measurement probe. Graubard also fails to provide a means for requesting from and communicating to an NDI system probe diagnostic and status information.
Accordingly, it would be advantageous to provide a wireless eddy current probe which has means to execute the advanced inspection functions required within common eddy current NDI operations. It would further be advantageous to provide a wireless eddy current probe which had means to provide diagnostic information to an NDI system to which it is wirelessly coupled.